Calcium ions to cross-link supramolecular nanofibers to tune the elasticity of hydrogels over orders of magnitude.

Learning from the stabilization of protein structures, we combine aromatic-aromatic and electrostatic interactions to tailor the elasticity of supramolecular hydrogels. Specifically, calcium ions allow interfiber cross-links among the supramolecular nanofibers of small peptides that consist of multiple carboxylic acid and aromatic groups. A small change in the concentration of calcium increases the elasticity of hydrogels over several orders of magnitude. This simple approach not only demonstrates a biomimetic design of materials but also confirms that the combination of multiple aromatic-aromatic interactions and multiple calcium salt bridges is a feasible way to control the mechanical properties of soft nanomaterials.